Low Prevalence of Lactase Persistence in Bronze Age Europe Indicates Ongoing Strong Selection over the Last 3,000 Years

 Lactase persistence (LP), the continued expression of lactase into adulthood, is the most strongly selected single

gene trait over the last 10,000 years inmultiple human populations. It has been posited that the primary allele

causing LP among Eurasians, rs4988235-A [1], only rose to appreciable frequencies during the Bronze and Iron

Ages [2, 3], long after humans started consuming milk from domesticated animals. This rapid rise has been

attributed to an influx of people from the Pontic-Caspian steppe that began around 5,000 years ago [4, 5].

We investigate the spatiotemporal spread of LP through an analysis of 14 warriors from the Tollense Bronze

Age battlefield in northern Germany ( 3,200 before present, BP), the oldest large-scale conflict site north of

the Alps. Genetic data indicate that these individuals represent a single unstructured Central/Northern European

population.We complemented these data with genotypes of 18 individuals fromtheBronzeAge siteMokrin

in Serbia ( 4,100 to  3,700 BP) and 37 individuals from Eastern Europe and the Pontic-Caspian Steppe region,

predating both Bronze Age sites ( 5,980 to 3,980BP).We infer lowLPin all three regions, i.e., in northern

Germany and South-eastern and Eastern Europe, suggesting that the surge of rs4988235 in Central and NorthernEuropewas

unlikely caused by Steppe expansions.We estimate a selection coefficientof 0.06 and conclude

that the selection was ongoing in various parts of Europe over the last 3,000 years.